Study of changes in composition and EELS ionization edges upon Ni4Ti3 precipitation in a NiTi alloy

Concentration gradients surrounding Ni4Ti3 Precipitates grown by appropriate annealing in a Ni(51)Ti(49)B2 austenite matrix are investigated by electron energy loss spectroscopy (EELS) and energy filtered transmission electron microscopy (EFTEM). Concentration gradients of similar to 1.0-2.0 at.% in Ni within the surrounding B2 matrix can be detected by both EELS and EFTEM, revealing a Ni depleted zone in the matrix. Besides the concentration gradients, the EELS integrated cross-section of the Ni L-2,L-3 edges for the Ni-depleted region increased slightly, when compared with a matrix region away from the precipitate and not depleted in Ni. (c) 2005 Elsevier Ltd. All rights reserved.